在自己的应用程序中安装Suave

Question

我有一个用c#编写的现有应用程序，并希望安装一个suave应用程序作为中间件，但由于我对f#相对较新，我发现很难导航这应该如何完成。我想我要找的是:

// in F# land
module MySuaveApp.ApiModule
let app =
  choose
    [ GET >=> choose
        [ path "/hello" >=> OK "Hello GET"
          path "/goodbye" >=> OK "Good bye GET" ]
      POST >=> choose
        [ path "/hello" >=> OK "Hello POST"
          path "/goodbye" >=> OK "Good bye POST" ] ]
  let getSuaveAsMiddleware() =
    ... magic goes here ...
// in Startup.cs
app.Use(MySuaveApp.ApiModule.getSuaveAsMiddleware())

至于这个魔法应该是什么，我认为它是OwinApp.ofAppFunc或OwinApp.ofMidFunc的组合，但我也想不出它应该是什么。

Answer 1

没有简单的魔术。¹ ofAppFunc和ofMidFunc是在这里创建WebPart s的OWIN组件，即OWIN -> Suave，而你想要的是Suave -> OWIN。

以下内容适用于您的"应用程序"，并作为使其工作所需的示例:

open System.Runtime.CompilerServices
[<Extension>]
module Api = 
    open Suave
    open Successful
    open Filters
    open Operators
    open Microsoft.Owin
    open System.Threading.Tasks
    let app = 
        choose [ GET >=> choose [ path "/hello" >=> OK "Hello GET"
                                  path "/goodbye" >=> OK "Good bye GET" ]
                 POST >=> choose [ path "/hello" >=> OK "Hello POST"
                                   path "/goodbye" >=> OK "Good bye POST" ] ]
    let withCtx (ctx : IOwinContext) webpart =
        async {
            let request =
                { HttpRequest.empty with
                    headers = ctx.Request.Headers |> List.ofSeq |> List.map (fun kvp -> kvp.Key, kvp.Value |> String.concat ",")
                    host = ctx.Request.Host.Value 
                    ``method`` = HttpMethod.parse ctx.Request.Method
                    url = ctx.Request.Uri }
            let! res = webpart { HttpContext.empty with request = request }
            res |> Option.iter (fun r ->
                ctx.Response.StatusCode <- r.response.status.code
                match r.response.content with
                | Bytes bs -> ctx.Response.Write bs
                | _ -> failwith "Not supported")
            return res
        }
    type SuaveMiddleware(n) =
        inherit OwinMiddleware(n)
        override __.Invoke(context : IOwinContext) =
            let res = withCtx context app |> Async.RunSynchronously
            match res with
            | Some _ -> Task.CompletedTask
            | None -> base.Next.Invoke context
    [<Extension>]
    let UseSuave(app : Owin.IAppBuilder) =
        app.Use(typeof<SuaveMiddleware>)

主要工作委托给withCtx，它尝试完成给定IOwinContext和WebPart的请求。它主要通过在Suave和OWIN上下文以及相关实体之间来回转换来实现这一点。注意，这段代码是一个PoC(概念验证)，不适合生产。如果Suave不能完成请求，SuaveMiddleware将请求转发给下一个中间件。

在c#中使用很容易:

using MySuave;
using Owin;
namespace Main
{
    using System.Web.Http;
    public class Startup
    {
        public static void Configuration(IAppBuilder appBuilder)
        {
            appBuilder.UseSuave();
            var config = new HttpConfiguration();
            config.MapHttpAttributeRoutes();
            appBuilder.UseWebApi(config);
        }
    }
}

给定

namespace Main.Example
{
    using System.Web.Http;
    [RoutePrefix("api")]
    public class ExampleController : ApiController
    {
        [HttpGet, Route("")]
        public string Index()
        {
            return "Hello World";
        }
    }
}

两个url都可以:

http://localhost:9000/hello

Hello GET

http://localhost:9000/api

   <string xmlns="http://schemas.microsoft.com/2003/10/Serialization/">Hello World</string>

_{¹至少我不知道。我很高兴被证明是错的}